Consolidated Statement of Comprehensive Income (Loss) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income from Continuing Operations	$ 106	$ 162	$ 162	$ 201
Other Comprehensive Income, Net of Taxes
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	10	1	10	1
Pension and other postretirement benefit plan activity, tax expense (benefit)	8	0	8	0
Other Comprehensive Income, Net of Taxes	10	1	10	1
Comprehensive Income from Continuing Operations	116	163	172	202
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests	1	1	3	3
Comprehensive Income from Continuing Operations Attributable to Ameren Corporation	115	162	169	199
Net Income (Loss) from Discontinued Operations	(10)	48	(209)	(394)
Other Comprehensive Income (Loss) from Discontinued Operations, Net of Taxes	(4)	4	(11)	19
Comprehensive Income (Loss) from Discontinued Operations	(14)	52	(220)	(375)
Less: Comprehensive Loss from Discontinued Operations Attributable to Noncontrolling Interest	0	(2)	0	(4)
Comprehensive Income (Loss) from Discontinued Operations Attributable to Ameren Corporation	(14)	54	(220)	(371)
Comprehensive Income (Loss)	$ 101	$ 216	$ (51)	$ (172)